This invention relates to dynamoelectric machines and more particularly to a brush holder and rigging assembly that prevents the brush holder from coming in contact with the commutator when the dynamoelectric machine is subjected to high shock forces.
Dynamoelectric machines that are used on board a ship can be subjected to very high shock forces which cause the rotor to move radially with respect to the stator. If the shock force is great enough the commutator bars can strike the brush holder with considerable force thereby causing damage to the commutator segments.
One possible solution to this problem is to mount the brush holders far enough away from the commutator so that the commutator cannot come in contact with the brush holders even when the dynamoelectric machine is subjected to a maximum anticipated shock force. This solution has been found to be unsatisfactory because a brush so held tends to be unstable during normal operation due to the increased extension of the brush from the brush holder to the commutator.
U.S. Pat. No. 2,679,606, Baudry et al, discloses a brush rigging assembly that minimizes the effect of certain disturbing vibrational forces that occur at particular frequencies. In Baudry et al, the brush rigging assembly includes an outer yoke member and a concentric inner yoke member. The inner yoke member is fastened rigidly to the base of the machine and the outer yoke member is resiliently mounted to the inner yoke by spring means. The brush holders are mounted on the movable outer yoke. The characteristic of the spring mounting means is such that the brush rigging assembly is resilient to the disturbing vibrational frequencies yet provides a substantial rigidity to any low frequency forces that tend to cause the brush rigging assembly to go out of alignment with respect to the axis of the commutator assembly. Baudry et al does not provide any means in addition to the spring suspension for absolutely limiting the relative motion of the commutator with respect to the brush holder.
It is, therefore, an object of this invention to provide an improved brush holder and rigging assembly for a dynamoelectric machine.
It is another object of this invention to provide a dynamoelectric machine in which the distance that the commutator can travel with respect to the brush holder is limited to a distance less than the normal clearance between the commutator segments and the end of the brush holder.